The replacement of traditional copper interconnects in integrated circuitry with optical data transfer mechanisms solves problems associated with signal integrity, communication speed and chip reliability, however, a reliable and suitable light source, which may be fabricated on silicon substrates and which is compatible with CMOS processing has not been available. A class of materials, e.g., rare earth-doped oxides, has been shown to be capable of emitting light when electrically excited. Different rare earth elements emit light of different wavelengths. The fabrication of such known devices has been performed by ion implantation and high temperature annealing processes, however, this technique lacks control over the depth and the dose of the rare earth ion implant, and does not have the ability to heal any damage induced by the requisite high-temperature treatment.
For rare earth-doped silicon-rich oxide (SRO) electroluminescent (EL) devices, high power electric fields must be applied during the injection of hot electrons into rare earth doped SROs, and high currents are required in order to generate sufficient quantities of electroluminescent photons. Therefore, high quality rare earth doped SROs must be deposited, and the process integration induced damage must be repaired.
Castagna et al., High efficiency light emission devices in silicon, Mat. Res. Soc. Symp, Vol. 770, (2003) demonstrated a working electroluminescent (EL) device using silicon-rich silicon oxide as the light emitting material. Silicon nano particle based-EL devices have been a focus of research because of compatibility with existing silicon-based IC industry processes. Undoped silicon nano particles produce a broad light spectrum because of wide particle size distribution, in a range of between about 1 nm to 10 nm. Rare earth doped SROs emit light at discrete wavelengths, corresponding to the intra 4 f transitions of the rare earth atoms. For example, the main emission wavelengths for terbium, ytterbium, and erbium doped SROs are located at wavelengths of 550 nm, 983 nm, and 1540 nm, respectively. The relative monochromaticity of the rare earth based light emission provides much better control of the wavelength and may have many applications in optical communications. To fabricate doped SROs, rare earth ion implantation is normally used, Castagna et al., supra, and Sun et al., Bright green electroluminescence from Tb3+ in silicon metal-oxide-semiconductor devices, J. Applied Physics 97 (2005). Although ion implantation provides purity and flexibility, it is expensive and limited by implantation dose. Dopant concentration vs depth is not uniform, and abrupt dopant concentration changes are not possible.
For rare earth doped nano-SRO EL devices, high power fields must be used for injection of hot electrons into the rare earth doped SRO, which generates the electroluminescence, hence, high quality rare earth doped SRO films have to be deposited, and the process integration induced damage must be removed.
Some of us have previously disclosed A method to make silicon nanoparticle from silicon rich oxide by DC reactive sputtering for electroluminescence application, Gao et al., U.S. patent application Ser. No. 11/049,594, filed Feb. 1, 2005, now abandoned.